Masonry bolt



April 28, 1931. A, c, wm 1,802,560

MASONRY BOLT Filed April 4, 1923 Fig].

I N VEN TOR.

ATTORNEYJ expansion shields,

Patented Apr. 28, 1931 ARTHUR C. KERWIN, OF NEW YORK, N. Y.

MASONRY 3 0m.

Application filed April 4, 1923. Serial No. 629,750.

The invention relates essentially to a bolt that will hold in masonry directly ditional by screwing it into the substance without any adhelp such as the employment of lead or wood plugs and other devices for gripping the bolt threads. An object of the invention is to provlde a bolt that will fasten itself into masonry when it is screwed home and will not be liable to loosen from vibration or usage.

The helix of the bolt is a spiral groove into the masonry designed to cut simply by turning it to the right until it is forced into the wall of the hole prepared for the bolt without damage to the masonry.

The invention resides more particularly in the novel combinations hereinafter described to the accompanymg and claimed, reference being made drawlngs m which Fig. 1 represents a side elevation of a bolt embodying this invention.

Fig. 2 is an inverted plan view of the same.

Fig.

3 is a side elevation of a modification showing the lower portion of a bolt. In the drawing the numeral 5 designates a shaft angular by an implement to rotate the shaft. head can be hexagonal as shown,

or stem which is provided with an head 6 whereby it can be gripped The or it could be square or oval with a notch to fit a screw driver.

A series of saw teeth 7 having acute angles 8 project from and form part of an integral the stem. The outlines of the teeth are helical surfaces inscribed about the stem in the shape of a spiral.

of the same diameter or a trifle smaller ally then a hole punched in masonry for its insertion. Each tooth is so shaped that the part 7 or nearly radially and the cutting first entering the hole is cut radially point 7 2 is nearly a right angle.

But as indicated in Fig. 3, the stem 9 can be tapered so as to work more freely in the hole. In this construction the ratchet threaded screw is also tapered to parallel the outline of the stem and cut into the masonry after a few turns of the stem.

As indicated in Fig. 2, each tooth has a The stem is usu- P different radius so that one will project less than the other and each has a blunt end or the ends could be pointed to more readily out a groove into vice each tooth is a triangle with a the masonry. In this depractically in the form of blunt top, while the front cutting edge thereof is substantially radial with the axis of the stem and the back forms an angle of about It will be understood, that the first tooth at the beginning of the spiral will make a slight cut and each successive tooth will follow the cut made by the tooth in front and by reason of the pitch of the helical or inclination of the te eth it forces itself into the inclined groove started by the first tooth.

Each tooth thus performs its function of cutting a portion of the spiral groove in the side of a hole initially formed in the stone. The first t projects the least cuts is formed in the of the bolt.

00th to enter the masonry and each successive tooth a little deeper until the spiral groove masonry to fit the thread The teeth are spaced by the serrations and being close together theywill provide a large number of cutting edges to bite into the wall of the hole and one tooth will follow the other in rapid succession.

I claim 1. A masonry b olt having a stem of practically the same diameter as a hole prepared for it in a section of masonry, and a series of triangular teeth helically located about the stem each having an acute angled back with radial forward cutting edge substantially forming a thread of relatively low itch for cutting a spiral groove in the wall of the hole to fasten the bolt by screwing it into the hole.

2. A masonry bolt having a tapered stem of practically the same diameter as a hole prepared for it in a section of masonry, and

a series of triangular teeth helically located about the stem angled back with radial edge and blunt outer end the stem substant relatively groove in the wal bolt by screwing 1 each including an acute forward cutting, projecting from ially forming a thread of low pitch for cutting a spiral l of the hole to fasten the i nto the hole.

3. A masonry bolt having a tapered stem of practically the same diameter as a hole prepared for it in a section of masonry, and a series of triangular teeth helically r cated about the stem of different radius each including an acute angled back with radial forward cutting edge and blunt outer end projecting from the stem, the diameter of the thread and stem increasing as the thread ad- 19 Vances along the stem vfor'cutting a spiral groove in the wall of the hole to fasten the bolt by screwing it into the hole. In testimony whereof I have hereunto set my hand. ARTHUR C. KER-WIN. 

